advertisement


Phono board options

How do you want the functionality split up

  • Four small boards

    Votes: 6 18.2%

  • Two boards, each a complete channel

    Votes: 13 39.4%

  • Two boards, stereo front end and stereo EQ

    Votes: 1 3.0%

  • One big board

    Votes: 11 33.3%

  • Don't care

    Votes: 2 6.1%
  • Total voters
    33
  • Poll closed .
PigletsDad.

Is there any problems or benfits of having a ground plane on both sides of the boards.

Sharif
 
Sharif,

Normally, ground plane on one side gives most of the shielding benefits, and leaves the other side free for tracking. You can put extra bits of ground copper between the tracks on the wiring side, but it makes almost no difference, as they are beside the signal tracks, not above or below them, and so they only block a negigible angle.

You really need to go to multi-layer boards if you want shielding both sides, so you can use the inner layers for wiring; this is not really practical for DIY construction, so one ground plane is a good compromise.

In practice, both my old hand made prototype, and the production Maclaren units were very quite when built with single ground planes..
 
PigletsDad said:
Sharif,

Normally, ground plane on one side gives most of the shielding benefits, and leaves the other side free for tracking. You can put extra bits of ground copper between the tracks on the wiring side, but it makes almost no difference, as they are beside the signal tracks, not above or below them, and so they only block a negigible angle.

You really need to go to multi-layer boards if you want shielding both sides, so you can use the inner layers for wiring; this is not really practical for DIY construction, so one ground plane is a good compromise.

In practice, both my old hand made prototype, and the production Maclaren units were very quite when built with single ground planes..
Click to expand...

Thanks for that, the copper plane will be made to the top-side of the board.
I will also be make a one-off for the MC pcb and MM pcb next weekend.

Sharif.
 
audioflyer said:
On a mirrored board layout the transistors may have to be rotated around to prevent the tracks from crossing over, or worst still a link being added to connect it to the relevant track.

Sharif.
Click to expand...


Ah I see, thanks. I told you I wouldn't know where to start :(
 
Just a little bit more progress.

MM board layout with copper plane.

http://www.mediafire.com/?411u8bgnhff8nxn

MM board layout without copper plane.

http://www.mediafire.com/?jri8vs2jj7zvv7u

Buffer board layout with copper plane.

http://www.mediafire.com/?y6n7zz5jgqzqi5e

Buffer board layout without copper plane.

http://www.mediafire.com/?cb9br93t8jv01dq

Again some pads are shown with no connected, don't worry they are connected to the top ground plane.

I'm hoping to make a couple of prototype pcb's for the MC & MM stages next weekend if all goes well.
I will not be prototyping the buffer board as layout is the same as the MM phonostage.

Sharif.
 
Hi Sharif,

Progress looks good. Any news on the prototypes? I'm looking to build a phono stage over the winter, probably inclide some form of input loading options, perhaps via relay controlled switches (thinking of adding a daughter board to your design if a group buy occurs).

Regards
 
Martin ask Sharif for that Hps5.1 board I sent him, I doubt he's so much as looked at it never mind finished it. ;-)
 
I think I may have a go at this board also, my intent would be to use PD's basic design with the following configuration:

MC input only
Current source on the gain stage
Switchable output, one regular RIAA and one with no correction to allow feeding into a DAC and RIAA correction via software
Relay selection of input impedence for MC (I know this adds some complexity and additional contacts, however I like the idea of being able to tweak the R without soldering and find the idea of loading plugs like Naim's Superline primitive)
Perhaps THAT matched transistor quads on the gain stage?
Selectable gain (via relay switching also)
Power will probably be via TPA Placid shunts.
This may be too complex a project but I'll give the board design a go over the holidays.

Any thoughts?
 
MartinC said:
Switchable output, one regular RIAA and one with no correction to allow feeding into a DAC and RIAA correction via software
Click to expand...

I've been thinking along these lines as well. What are you thinking in terms of ADC and software?

And yes, I'm game for a build.
 
I'm using a Beiss AD24QS with a few mods. The Beiss is available as a kit and works extremely well. For software, not too sure, but I belive that PureVinyl for the Mac will perform the RIAA conversion. Probably PureMusic with a suitable plug in would also convert on playback.

Can't promise anything here, and it may well take me a while to get the board designed, with some help from folks here.

Cheers!
 
Thanks for the tip on the Beiss, Martin. Wow, it's even a kit at a very reasonable price. This sounds like a fun project.
 
Yeah, Uwe Beiss is a great guy, and the kit is very complete. I bought the upgraded version from him, and also changed out the MK2703 clock synthesizer for a MK2703B that has lower jitter.
 
I am not keen on the idea of software RIAA. For all types of ADC the accuracy falls the more rapidly the input signal changes; in the case of the multiloop, high order sigma delta converters that are used nowadays, this goes as some high power of the rate of change; for quasi static signals, they are near perfect.

Hardware RIAA is basically a treble cut and bass boost, and makes life vastly easier for the following digitisation.

I am not keen on your idea of relay switched loads - it adds lots of contacts to the ultra-low level signal section, and greatly extends the size of the pickup loops for the low level signal, making shielding much harder. My preferred method is to have some parallel loading plugs, to explore the tradeoffs, then solder the optimum values in place.

But it is a free world, and good luck with the idea.
 
Thanks for the input PD, it's early in the project so changes are likely! - One question I woud have relates to the input transistors. The Toshiba ones in the original circuit are long obsolete, and from googling it would appear that there are now no equivalent replacements. There also seem to be questions as to whether the THAT semiconductor arrays are suitable, so I think an alternate route may be called for...

Regards

Martin
 
Actually, the input transistors were/are from Hitachi, now Renesas. You can buy them easily - RS and Dalbani both have them.

RS part numbers are 197-9834 and 197-9840. Both show as temporarily out of stock; the 1085 is due in Boxing day. Dalbani have stock but are slightly more expensive.

The THAT ones have much more noise.
 
Thanks PD. I didn't see the Rensas versions being available here in the US through any of the normal channels, but if RS have them listed then Newark should too, I'll look again. I did notice the noise figures of the THAT components are high. I may try a couple of routes, perhaps your design as well as a Phonoclone IC based one. This is more of a fun project than a need, I am seeing if and DIY designs will compete with my Linto.

Cheers and thanks for the help!

Update: Looks like RS won't export anymore and none of the US outlets appear to carry the parts, including Dalbani in the US and RS's US affiliate Allied. So unfortunately a dead end...
 
MartinC said:
Thanks PD. I didn't see the Rensas versions being available here in the US through any of the normal channels, but if RS have them listed then Newark should too, I'll look again. I did notice the noise figures of the THAT components are high. I may try a couple of routes, perhaps your design as well as a Phonoclone IC based one. This is more of a fun project than a need, I am seeing if and DIY designs will compete with my Linto.

Cheers and thanks for the help!

Update: Looks like RS won't export anymore and none of the US outlets appear to carry the parts, including Dalbani in the US and RS's US affiliate Allied. So unfortunately a dead end...
Click to expand...

Hi Martin

I am happy to purchase and send out to you or bring over as I am in the US most months
 
You must log in or register to reply here.


advertisement


Back
Top